1. Field of the Invention
The present invention relates to a tape-type magnetic recording medium for use in a shield-type magnetoresistance effect magnetic head, a method of manufacturing the tape-type magnetic recording medium and a method of reproducing a signal from the tape-type magnetic recording medium by using the shield-type magnetoresistance effect magnetic head.
2. Description of Related Art
In a filed of magnetic recording, dense recording has been required year by year because of enlargement of the quantity of information which must be recorded. As a result, magnetic recording mediums have been changed from so-called coating-type magnetic recording mediums of a conventional type having a structure, in which magnetic particles to be applied are dispersed in a binder, to so-called thin-film-type magnetic recording mediums having a structure in which a ferromagnetic metal film is formed by plating or vacuum thin-film forming means (a vacuum evaporation method, a sputtering method, an ion plating method or the like).
Since the thin-film magnetic recording medium having the formed ferromagnetic metal film exhibits large coercive force and excellent square ratio and capable of eliminating a necessity of mixing, to the magnetic layer thereof, a binder which is a non-magnetic material as has been required for the coating-type magnetic recording medium, the filling density of the magnetic material (namely, the quantity of magnetization per unit volume) can significantly be raised. Moreover, the thin-film magnetic recording medium is able to considerably reduce the thickness of the magnetic layer as compared with the coating-type magnetic recording medium. Therefore, an excellent electromagnetic conversion characteristic can be realized in the short wavelength region. In addition, the thin-film magnetic recording medium has another characteristic in that demagnetization occurring during a recording operation can significantly be prevented. Since the thin-film magnetic recording medium has various advantages as compared with the coating-type magnetic recording medium as described above, it can be considered that the thin-film magnetic recording mediums will be a main portion of the high density magnetic recording mediums.
In the industrial field of the magnetic recording, the thin-film magnetic recording medium has been in the form of a tape-type magnetic recording medium having a magnetic layer formed by a diagonal evaporation method. The tape-type magnetic recording medium formed by the diagonal evaporation method is formed by depositing a magnetic metal material on a moving non-magnetic support member (which is a polymer film, such as a polyester film, a polyamide film or a polyamide film) from a diagonal direction by the vacuum evaporation method. The tape-type magnetic recording medium formed by the diagonal evaporation method has a structure such that magnetic particles are oriented diagonally with respect to the surface of the non-magnetic support member. Therefore, higher recording can be performed as compared with the conventional magnetic tape in which the magnetic particles are oriented in the lengthwise direction. Specifically, the above-mentioned tape-type magnetic recording medium has a structure that the axis of easy magnetization in the magnetic layer is inclined by about 20.degree. from the surface of the non-magnetic support member.
To meet the requirement for raising the density in recording, the magnetic head must be improved as well as the improvement in the magnetic recording medium. In particular, a reproducing method adapted to a magnetoresistance effect magnetic head (hereinafter called an "MR head") using the magnetoresistance effect device has attracted attention.
The MR head is a magnetic head using the magnetoresistance effect and thus capable of detecting a signal having a lower level. Therefore, the MR head is able to be used even if the magnetic field of the signal is reduced because of shortening of the recording wavelength caused from high density recording.
However, optimum conditions for the operation for reproducing the tape-type magnetic recording medium by using the MR head have not been investigated. Thus, a satisfactory high density recording operation has not been performed.